Exhaust gas recirculation (EGR) is used in internal combustion engines for reducing emissions in many gasoline and diesel engines. EGR recirculates a portion of an engine's exhaust gas back to the engine cylinders by intermixing incoming air with recirculated exhaust gas. This dilutes the mix with inert gas such that the exhaust gases displace some of the normal air intake. This lowers the peak combustion temperature in the cylinders, since exhaust gases have already combusted and do not burn again when recirculated. Nitrous oxide forms much faster at higher temperatures, and EGR thus limits the formation of nitrous oxide by slowing and cooling the combustion process.
Engines using EGR for emissions reduction may have some EGR exhaust gas products undesirably ingested into other components, such as an air compressor. Air compressors are often used in vehicle applications to compress air for use in pneumatic brakes, for example. Some of the EGR gas products can be ingested through the air compressor supply port that is provided in the same intake connection used for air that is mixed with the EGR gas. If a significant amount of EGR is ingested, it can cause reduced service life of the air compressor and related components.
To reduce the amount of EGR ingested by the air compressor, the entry to the air compressor supply port has sometimes been moved upstream, away from the entry port of the EGR gas, by extending a “hood” over the air compressor port in the direction away from the EGR gas entry. In some cases, a tube is inserted into the end of the hood to further extend the air supply port upstream. This tube extends into the air connection inlet elbow. However, the tube cannot be extended very far into the elbow before it limits the allowable rotation of the elbow. Rotation of the elbow is needed for flexibility in allowing different engine configurations of different manufacturers to be connected to the elbow; e.g., such different configurations may have components connecting to the elbow at different angles and orientations.
Furthermore, placing the air compressor supply port further upstream in the vehicle plumbing is discouraged due to the expense incurred by the vehicle manufacturer and the variability in the designs that may affect air compressor operation.
Accordingly, a system and method that allows full rotation of the inlet elbow and also allows for the air compressor inlet port to be moved further upstream from the EGR ports than allowed by previous designs would be desirable in many applications.